Reducing energy demand in Castelvetrano-style table olive production through Candida-based bioprotection approach

Abstract

The traditional Castelvetrano method for producing Nocellara del Belice green table olives relies on prolonged refrigeration, often up to 180 days, to ensure microbiological stability and preserve desirable sensory attributes, resulting in substantial energy consumption. This study evaluated whether the use of two bioprotective yeasts, Candida boidinii LC1 and Candida norvegica OC10, could enable a 50% reduction in refrigeration time without compromising product quality. Olives were processed under nine experimental conditions combining different temperature regimes and inoculation strategies. Microbiological, physicochemical, volatile, and sensory parameters were monitored for 180 days. Refrigeration remained the primary barrier against spoilage microorganisms. However, yeast inoculation significantly reduced populations of Enterobacteriaceae, Pseudomonadaceae, and Staphylococcaceae, thereby enhancing microbiological stability under the tested conditions. Under refrigerated or combined treatments, the inoculated strains dominated the microbial community (>94%). Inoculated olives exhibited increased pulp firmness (up to 23.12 kg/cm²), a more intense green colour, and more complex aromatic profiles mainly associated with esters and aromatic alcohols. Sensory panels indicated higher perceived sweetness, crispness, and overall acceptance. Importantly, shortening refrigeration from 180 to 90 days did not adversely affect the quality of inoculated olive batches. Targeted use of C. boidinii LC1 and C. norvegica OC10 therefore emerges as a promising bioprotective strategy that supports microbiological stability, defined as controlled microbial proliferation, while preserving sensory quality under the tested conditions, and suggests the potential for reduced energy use and environmental impact in the Castelvetrano method. The reduction in refrigeration time implies possible energy savings and lower CO₂ emissions. However, these estimates are based on a simplified modelling approach and should be considered indicative. Overall, the proposed strategy aligns with cleaner production goals and contributes to SDG 12 by reducing refrigeration duration and associated energy demand within the limits of a model based assessment.